The pressure reducer of the invention is the type comprising an inlet valve, an outlet valve and a gas by-pass valve, and is characterised by the special arrangement and conformation of the parts, which makes it safer to use than similar known types. In addition, it guarantees constant outflow pressure regardless of the gas pressure fed into the reducer, this being essential to allow precise carburetion regulation under any operating conditions.
In order to feed liquid or compressed gases to internal combustion engines, a device must be installed prior to the engine feed apparatus which reduces the pressure of the gas arriving from the tank (which in the case of compressed gases can reach values of over 200 atmospheres) to a value generally lower than one atmosphere. To ensure proper operation of the engine under any conditions, the pressure at the reducer outlet should be kept as constant as possible.
This problem has not yet been fully solved with known pressure reducers, especially in the case of compressed gas feed, where the pressure varies within an extremely wide range.
FIG. 1 shows a diagram of the conventional type of pressure reducer, in which high-pressure gas enters through a pipe 1, closed by a valve 2, and exits through a pipe 3.
A flexible diaphragm 4 is fitted inside the reducer; a cap 5 is fixed to the diaphragm, and a helical spring 6 acts on the cap, tending to push the diaphragm downwards.
A pin 7 is fixed to the diaphragm; this pin operates on the end of a lever 8 with central fulcrum 9. Valve 2 is fitted at the opposite end of the said lever.
The force F exerted by spring 6 tends to keep valve 2 open, allowing gas to pass through it.
As the pressure in the reducer increases, it pushes diaphragm 4 upwards against spring 6, closing valve 2.
The operation of the reducer is governed by the following equation: EQU (P.times.s.times.a)+(F.times.b)=(p.times.S),
where:
S=area of diaphragm PA1 p=pressure inside reducer PA1 s=area of pipe 1 PA1 P=pressure of gas entering reducer PA1 F=force exerted by spring 6 PA1 a,b=arms of lever 8, as shown in the diagram.
In this equation the only variables are P and p. This means that the pressure inside the reducer, and thus at the reducer outlet, depends on the pressure at the reducer inlet which, as already mentioned, varies considerably depending on the level to which the tank is filled. This makes it impossible to obtain optimum engine feed regulation suitable for any running conditions and any tank level.
Pressure reducers comprise (or are coupled to) a by-pass valve designed to cut off the gas supply. This valve must remain in the closed position when the installation is not in operation.
In known types of solenoid valve (one of which is illustrated in the diagram shown in FIG. 2), high-pressure gas arriving from a pipe 10 flows to a chamber 11, from which it exits through a nozzle 12.
This nozzle is closed by a valve 13 which slides inside a seating 14 (not airtight), surrounded by an electromagnet 15.
A spring 16 tends to press the valve downwards, to keep it closed.
Valve 13 is kept pressed downwards in the closed position by the pressure of the gas flowing from chamber 11 to seating 14.
While this configuration is necessary for safety reasons because the valve must be designed to remain closed when not operating, it involves some drawbacks; in order to open the valve, considerable force needs to be exerted to overcome the gas pressure on valve 13 which, as mentioned, often exceeds 200 atmospheres.
This means fitting a sufficiently powerful electromagnet which will therefore be large, costly and present high current absorption.
To overcome this difficulty, manufacturers often fit this solenoid valve after the pressure reducer, where the gas pressure is generally under 0.5 atmospheres. This system allows valve control with minimal energy absorption, although it presents the drawback that high gas pressure still remains in some parts of the reducer, located prior to the valve, even when the installation is not in operation.
U.S. Pat. No. 3,960,126 illustrates a liquid gas pressure regulator divided internally into three chambers by a pair of diaphragms.
The diaphragms are connected by a spring fitted between them.
The first chamber contains a valve opened by the first membrane to regulate the incoming gas.
The second diaphragm is sensitive to the negative pressure created in the third chamber, connected to the carburettor. Variations in the position of the second diaphragm affect the first, to which it is connected via the spring, thereby controlling the operation of the valve located in the first chamber so as to adapt the gas pressure in the reducer to the engine rotation speed.
This type of pressure reducer still does not solve the problems referred to above; equally, its construction is extremely complex, and it is therefore subject to breakdowns.